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Help, VFD E-Stop


Dec 6, 2008
Dartmouth, MA
A few months ago I decided to convert my milling machine to three phase using a 220v single phase to 220v three phase inverter. I bought a very popular inverter off Amazon. Wired it up and it is an amazing improvement to my shop. I liked it so much I just received the exact same components to convert my lathe. I have no issue using the control panel to operate all the functions I want by mounting it remotely. But I need some type of emergency stop as the "stop" button is way too small for an emergency situation. I ordered an E-Stop module from Amazon. But try as I may, I can't figure out how to install it to effectively stop the machines in an emergency. The switch itself is rated 200v/3a so with the VFD drawing around 9 amps, I can't just insert it into the power wiring. I'd rather not incorporate a magnetic relay/switch. So I want to connect it via the VFD but still have control of the attached control panel functions. Can anyone explain to me how to accomplish this. Thanks!


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That VFD is pretty questionable.... Probably the "brand not discussed here" (very popular on Amazon).

But the question applies to most VFDs so no issues.

Real e-stop capabilities actually cut power, and do not depend on a chain of things working correctly.

Some VFDs have an "STO" feature (safe torque off) that allows cutting power to the output devices, which positively shuts down the output. UL accepts that.
These cheaper VFD's are a little funny to wire a estop. What you need is a Estop button with normally open contact and hook up the estop in parallel with the stop command. It needs to hold the contact closed or the machine will start up again when you release the estop.
Wiring a normally-open switch to a programmable VFD input and calling it an 'e-stop' breaks every rule in the book. If the wire breaks, parameters get changed, or the drive just decides to factory reset itself, your e-stop silently fails.

If the drive only draws 9A, just wire a cheap paddle switch into the drive input power and call it a day.